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Addition of Alloying Agents to Improve the Performance of Zn/Al Metallic Coated Steel / MATHEW GOLDSWORTHY

Swansea University Author: MATHEW GOLDSWORTHY

  • E-Thesis under embargo until: 18th December 2029

DOI (Published version): 10.23889/SUThesis.69583

Abstract

This work set out to investigate the microstructural changes and corrosion mechanisms of several zinc-based sacrificial metallic coatings which are used within the strip steel industry. The assessment of alloying additions at various compositions to determine what microstructural features and phase...

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Published: Swansea University, Wales, UK 2024
Institution: Swansea University
Degree level: Doctoral
Degree name: EngD
Supervisor: Sullivan, J.
URI: https://cronfa.swan.ac.uk/Record/cronfa69583
first_indexed 2025-05-29T12:37:49Z
last_indexed 2025-05-30T06:10:17Z
id cronfa69583
recordtype RisThesis
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This has the potential to reduce raw material usage and improve the environmental impact / carbon footprint of galvanised coatings, extend the surface life and save the manufacturer money by reducing maintenance costs.Chapter 3 uses Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometry (EDS) to evaluate the microstructure and phase morphologies present within several industry-made metallic coatings. Time-lapse microscopy (TLM) and Scanning Vibrating Electrode Technique (SVET) are used to understand and determine the corrosion mechanism of each coating when immersed in salt solution.Both TLM and SVET determined that higher weight percentages of aluminium in zinc-aluminium (ZA) coatings led to enhanced corrosion protection. Higher weight percentages of aluminium and magnesium in the zinc-aluminium-magnesium (ZMA)system also led to improved corrosion performance in salt solution.Chapter 4 investigated, using TLM and Linear Polarisation Resistance (LPR) the corrosion rate of the same industrially made metallic coatings but in both 0.45 wt.%NaCl and Prohesion solution (0.4 wt.% Ammonium sulphate, 0.05 wt.% NaCl). This assessed the effect of ammonium ions on ZMA coatings when compared to non-magnesium-containing. TLM illustrated a change in corrosion mechanism from local corrosion to general corrosion when immersed in a dilute salt solution compared with Prohesion solution respectively. LPR experiments confirmed that the presence of magnesium had a detrimental effect on the corrosion rate of metallic coatings and that aluminium offered resistance to corrosive ammonium ions. The addition of Benzotriazole into Prohesion solution offered protection against ammonium ions for ZMA coatings.Chapter 5 utilises microstructural analysis techniques, TLM, SVET and LPR techniques to assess the effect of coating weight (g.m-2) on the microstructure and corrosion performance of MagiZinc samples produced using the ZODIAC (Zinc and Other Developments in Alloy Coatings) galvanising line. It was found that the volume fraction of the primary Zn phase reduced with increased coating weights do to varying cooling rates of the ZMA coatings. SVET and LPR showed an increase in coating thickness resulting in a significant increase in performance due to a change in corrosion mechanism. The anodic growth mechanism for ZMA310 (310 g.m-2) was more localised and constrained compared to ZMA80 (80 g.m-2).Chapter 6 followed on from the previous chapter and investigated the effect of cooling rate on MagiZinc samples. Samples were produced using a hot dip simulator at several cooling rates and microstructural analysis techniques, TLM, SVET and LPR techniques were used to assess changes in microstructure and corrosion performance.It was found that faster-cooled samples lead to a reduction in the formation of binary eutectic and an increase in the formation of ternary eutectic. This results in an improved corrosion rate when more ternary eutectic is present within the microstructure.In summary, the diverse behaviours observed in different coatings underscore the importance of understanding their microstructures, corrosion mechanisms, and the influence of alloying elements. 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spelling 2025-05-29T13:41:12.6438076 v2 69583 2025-05-29 Addition of Alloying Agents to Improve the Performance of Zn/Al Metallic Coated Steel e98e4b6ebc37087c4870fad3c7feca63 MATHEW GOLDSWORTHY MATHEW GOLDSWORTHY true false 2025-05-29 This work set out to investigate the microstructural changes and corrosion mechanisms of several zinc-based sacrificial metallic coatings which are used within the strip steel industry. The assessment of alloying additions at various compositions to determine what microstructural features and phase formations lead to superior performance in a corrosive environment. This has the potential to reduce raw material usage and improve the environmental impact / carbon footprint of galvanised coatings, extend the surface life and save the manufacturer money by reducing maintenance costs.Chapter 3 uses Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometry (EDS) to evaluate the microstructure and phase morphologies present within several industry-made metallic coatings. Time-lapse microscopy (TLM) and Scanning Vibrating Electrode Technique (SVET) are used to understand and determine the corrosion mechanism of each coating when immersed in salt solution.Both TLM and SVET determined that higher weight percentages of aluminium in zinc-aluminium (ZA) coatings led to enhanced corrosion protection. Higher weight percentages of aluminium and magnesium in the zinc-aluminium-magnesium (ZMA)system also led to improved corrosion performance in salt solution.Chapter 4 investigated, using TLM and Linear Polarisation Resistance (LPR) the corrosion rate of the same industrially made metallic coatings but in both 0.45 wt.%NaCl and Prohesion solution (0.4 wt.% Ammonium sulphate, 0.05 wt.% NaCl). This assessed the effect of ammonium ions on ZMA coatings when compared to non-magnesium-containing. TLM illustrated a change in corrosion mechanism from local corrosion to general corrosion when immersed in a dilute salt solution compared with Prohesion solution respectively. LPR experiments confirmed that the presence of magnesium had a detrimental effect on the corrosion rate of metallic coatings and that aluminium offered resistance to corrosive ammonium ions. The addition of Benzotriazole into Prohesion solution offered protection against ammonium ions for ZMA coatings.Chapter 5 utilises microstructural analysis techniques, TLM, SVET and LPR techniques to assess the effect of coating weight (g.m-2) on the microstructure and corrosion performance of MagiZinc samples produced using the ZODIAC (Zinc and Other Developments in Alloy Coatings) galvanising line. It was found that the volume fraction of the primary Zn phase reduced with increased coating weights do to varying cooling rates of the ZMA coatings. SVET and LPR showed an increase in coating thickness resulting in a significant increase in performance due to a change in corrosion mechanism. The anodic growth mechanism for ZMA310 (310 g.m-2) was more localised and constrained compared to ZMA80 (80 g.m-2).Chapter 6 followed on from the previous chapter and investigated the effect of cooling rate on MagiZinc samples. Samples were produced using a hot dip simulator at several cooling rates and microstructural analysis techniques, TLM, SVET and LPR techniques were used to assess changes in microstructure and corrosion performance.It was found that faster-cooled samples lead to a reduction in the formation of binary eutectic and an increase in the formation of ternary eutectic. This results in an improved corrosion rate when more ternary eutectic is present within the microstructure.In summary, the diverse behaviours observed in different coatings underscore the importance of understanding their microstructures, corrosion mechanisms, and the influence of alloying elements. These insights are crucial for the development of advanced coatings with enhanced corrosion resistance which contribute to the longevity and durability of materials in various environmental conditions. E-Thesis Swansea University, Wales, UK Engineering 18 12 2024 2024-12-18 10.23889/SUThesis.69583 COLLEGE NANME COLLEGE CODE Swansea University Sullivan, J. Doctoral EngD Tata Steel UK, EPSRC doctoral training grant Tata Steel UK, EPSRC doctoral training grant 2025-05-29T13:41:12.6438076 2025-05-29T13:29:07.8312011 Faculty of Science and Engineering School of Engineering and Applied Sciences - Materials Science and Engineering MATHEW GOLDSWORTHY 1 Under embargo Under embargo 2025-05-29T13:37:12.2077102 Output 15308674 application/pdf E-Thesis true 2029-12-18T00:00:00.0000000 Copyright: The Author, Mathew Goldsworthy, 2023 true eng
title Addition of Alloying Agents to Improve the Performance of Zn/Al Metallic Coated Steel
spellingShingle Addition of Alloying Agents to Improve the Performance of Zn/Al Metallic Coated Steel
MATHEW GOLDSWORTHY
title_short Addition of Alloying Agents to Improve the Performance of Zn/Al Metallic Coated Steel
title_full Addition of Alloying Agents to Improve the Performance of Zn/Al Metallic Coated Steel
title_fullStr Addition of Alloying Agents to Improve the Performance of Zn/Al Metallic Coated Steel
title_full_unstemmed Addition of Alloying Agents to Improve the Performance of Zn/Al Metallic Coated Steel
title_sort Addition of Alloying Agents to Improve the Performance of Zn/Al Metallic Coated Steel
author_id_str_mv e98e4b6ebc37087c4870fad3c7feca63
author_id_fullname_str_mv e98e4b6ebc37087c4870fad3c7feca63_***_MATHEW GOLDSWORTHY
author MATHEW GOLDSWORTHY
author2 MATHEW GOLDSWORTHY
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college_str Faculty of Science and Engineering
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hierarchy_top_id facultyofscienceandengineering
hierarchy_top_title Faculty of Science and Engineering
hierarchy_parent_id facultyofscienceandengineering
hierarchy_parent_title Faculty of Science and Engineering
department_str School of Engineering and Applied Sciences - Materials Science and Engineering{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Engineering and Applied Sciences - Materials Science and Engineering
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description This work set out to investigate the microstructural changes and corrosion mechanisms of several zinc-based sacrificial metallic coatings which are used within the strip steel industry. The assessment of alloying additions at various compositions to determine what microstructural features and phase formations lead to superior performance in a corrosive environment. This has the potential to reduce raw material usage and improve the environmental impact / carbon footprint of galvanised coatings, extend the surface life and save the manufacturer money by reducing maintenance costs.Chapter 3 uses Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometry (EDS) to evaluate the microstructure and phase morphologies present within several industry-made metallic coatings. Time-lapse microscopy (TLM) and Scanning Vibrating Electrode Technique (SVET) are used to understand and determine the corrosion mechanism of each coating when immersed in salt solution.Both TLM and SVET determined that higher weight percentages of aluminium in zinc-aluminium (ZA) coatings led to enhanced corrosion protection. Higher weight percentages of aluminium and magnesium in the zinc-aluminium-magnesium (ZMA)system also led to improved corrosion performance in salt solution.Chapter 4 investigated, using TLM and Linear Polarisation Resistance (LPR) the corrosion rate of the same industrially made metallic coatings but in both 0.45 wt.%NaCl and Prohesion solution (0.4 wt.% Ammonium sulphate, 0.05 wt.% NaCl). This assessed the effect of ammonium ions on ZMA coatings when compared to non-magnesium-containing. TLM illustrated a change in corrosion mechanism from local corrosion to general corrosion when immersed in a dilute salt solution compared with Prohesion solution respectively. LPR experiments confirmed that the presence of magnesium had a detrimental effect on the corrosion rate of metallic coatings and that aluminium offered resistance to corrosive ammonium ions. The addition of Benzotriazole into Prohesion solution offered protection against ammonium ions for ZMA coatings.Chapter 5 utilises microstructural analysis techniques, TLM, SVET and LPR techniques to assess the effect of coating weight (g.m-2) on the microstructure and corrosion performance of MagiZinc samples produced using the ZODIAC (Zinc and Other Developments in Alloy Coatings) galvanising line. It was found that the volume fraction of the primary Zn phase reduced with increased coating weights do to varying cooling rates of the ZMA coatings. SVET and LPR showed an increase in coating thickness resulting in a significant increase in performance due to a change in corrosion mechanism. The anodic growth mechanism for ZMA310 (310 g.m-2) was more localised and constrained compared to ZMA80 (80 g.m-2).Chapter 6 followed on from the previous chapter and investigated the effect of cooling rate on MagiZinc samples. Samples were produced using a hot dip simulator at several cooling rates and microstructural analysis techniques, TLM, SVET and LPR techniques were used to assess changes in microstructure and corrosion performance.It was found that faster-cooled samples lead to a reduction in the formation of binary eutectic and an increase in the formation of ternary eutectic. This results in an improved corrosion rate when more ternary eutectic is present within the microstructure.In summary, the diverse behaviours observed in different coatings underscore the importance of understanding their microstructures, corrosion mechanisms, and the influence of alloying elements. These insights are crucial for the development of advanced coatings with enhanced corrosion resistance which contribute to the longevity and durability of materials in various environmental conditions.
published_date 2024-12-18T05:28:35Z
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score 11.089386

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